Topological string theory from D-brane bound states
Abstract
We investigate several examples of BPS bound states of branes and their associated topological field theories, providing a window on the nonperturbative behavior of the topological string. First, we demonstrate the existence of a large N phase transition with respect to the 't Hooft coupling in q-deformed Yang-Mills theory on S2. The Ooguri-Strominger-Vafa [62] relation of this theory to topological strings on a local Calabi-Yau [7], motivates us to investigate the phase structure of the trivial chiral block at small Kahler moduli. Second, we develop means of computing exact degeneracies of BPS black holes on certain toric Calabi-Yau manifolds. We show that the gauge theory on the D4 branes wrapping ample divisors reduces to 2D q-deformed Yang-Mills theory on necklaces of P1's. At large N the D-brane partition function factorizes as a sum over squares of chiral blocks, the leading one of which is the topological closed string amplitude on the Calabi-Yau, in agreement with the conjecture of [62]. Third, we complete the analysis of the index of BPS bound states of D4, D2 and D0 branes in IIA theory compactified on toric Calabi-Yau, demonstrating that they are encoded in the combinatoric counting of restricted three dimensional partitions. We obtain a geometric realization of the torus invariant configurations as a crystal associated to the bound states of 0-branes at the singular points of a single D4 brane wrapping a high degree equivariant surface that carries the total D4 charge. The crystal picture provides a direct realization of the OSV relation to the square of the topological string partition function, which in toric Calabi-Yau is also equivalent to a theory of three dimensional partitions. Finally, we apply the techniques of the quiver representation of the derived category of coherent sheaves to discover a topological matrix model for the index of BPS states of D2 and D0 branes bound to a 6-brane. This enables us to examine the quantum foam [37] description of the A-model by embedding it in the full string theory.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 2007
- Bibcode:
- 2007PhDT........27J